1. Field of the Disclosure
This disclosure relates generally to data communication between rotating and non-rotating members of downhole tools used for drilling wellbores.
2. Background of the Art
Oil wells (also referred to as “wellbores” or “boreholes”) are drilled with a drill string that includes a tubular member having a drilling assembly (also referred to as the “bottomhole assembly” or “BHA”) attached to its bottom end. Drilling assemblies typically include devices and sensors that provide information about a variety of parameters relating to the drilling operations (“drilling parameters”), behavior of the drilling assembly (“drilling assembly parameters” or “BHA parameters”) and the formation surrounding the wellbore (“formation parameters”). A drill bit attached to the bottom end of the drilling assembly is rotated by rotating the drill string and/or by a drilling motor (also referred to as a “mud motor”) in the BHA to disintegrate the rock formation to drill the wellbore. A large number of wellbores are drilled along contoured trajectories. For example, a single wellbore may include one or more vertical sections, deviated sections and horizontal sections through differing types of rock formations. Some drilling assemblies include a non-rotating or substantially non-rotating sleeve outside a rotating drill collar. A number of force application members on the sleeve are extended to apply selective force inside the wellbore to alter the drilling direction to drill the wellbore along a desired well path or trajectory. The non-rotating sleeve includes electrical and electronics components, such as motors, sensors and electronics circuits for processing of data. U.S. Pat. No. 6,540,032, issued to the assignee of this application, which is incorporated herein by reference in its entirety, discloses an exemplary drilling assembly in which both power and data between the rotating and non-rotating members are transmitted via an inductive coupling device, such as an inductive transformer, wherein the data signals are modulated onto the power signals. Such a method, in some aspects, may be limited in bandwidth. The data signals also may be corrupted by the noise generated by the inductive transformer. Therefore, there is a need for an improved data communication apparatus and method for transferring data signals between rotating and non-rotating members of downhole tools.